APPENDIX. 405 



ADDENDA. 



The publication of tlio foregoing memoir led to several letters 

 being addressed to tlie author on topics connected with it. Some 

 of these were from gentlemen eminent in science or politics, whose 

 opinions are entitled to the highest respect. Extracts are given 

 from such only as introduce new data, either of fact or opinion. 



Geological Theoeies. — Professor Dewey, of Williams Col- 

 lege, observes: "A friend has just lent me your 'Memoir on a 

 Fossil-Tree.' Though the account is very interesting, I do not 

 perceive its exact bearing on the Neptunian and Plutonian hypo- 

 theses. The fault is doubtless in me, and you will excuse my 

 remarks and set me right. I had supposed the Huttonians and 

 "Wernerians did not dispute about the manner in which the se- 

 condary rocks w^ere formed. Macculloch, and others before him, 

 led me into this opinion, though it may be erroneous. But 

 Bakewell, who is referred to as authority in Rees's Cyclo]}ccdia^ 

 says, p. 131: 'Geologists are agreed that secondary rocks have 

 been formed by the agency of water.' If this be so, they would 

 agree generally with the account of Dr. Cooper respecting the 

 formation of petrifactions, and especially those of vegetables, and 

 the fossil-tree would be treated of in a similar manner by both." 



Hutton's original hypothesis, and not the modifications of it 

 introduced by the Neptu-Yulcanists, were adverted to in reply. 

 Subsequently, Professor Dewey writes": — 



"I was greatly obliged by your letter in various respects, and I 

 write you now to make my acknowledgments for it, as well as to 

 maintain the correctness of your notions on the Huttonian hypo- 

 thesis. As you had seen a Scotch mineralogist directly from the 

 mint of Playfair, I had every reason to suppose you had received 

 correct views of Playfair's notions on the subject. I have been 

 led, therefore, to examine the matter, and, as I may have set you 

 on the search, I wish to prevent your continuing it on my ac- 

 count, or from what I wrote. 



"Playfair's Illustrations I have never seen. Occasional ex- 

 tracts, or allusions to its points, have fallen in my way. But I 

 have before me a very full abstract of Hutton's paper on the sub- 

 ject, from the Transactions of the Boyal Society of Edinburgh. It 



